Phase 4: legal-to-finance domain swap bundled with the Mike-to-Gordon rename

Archibald312's Phase 4 PR reframes the fork as a finance AI assistant - M&A diligence, private equity, private credit, leveraged finance, and equity research - while finishing the Mike-to-Gordon rename. The two changes share enough surface area (system prompts, type identifiers, MIME types, copy) that bundling them in one PR avoids a redundant second sweep.

The domain swap lands in the prompts and the taxonomy. The main chat system prompt, the project-context block, tabular extraction and review prompts, and the docx-generation tool description are all rewritten for finance work, with citation auditability foregrounded. The practice-area list is fully replaced: 19 legal practices removed, 17 finance verticals added. Column presets are handled additively - neutral contract columns stay because they apply to finance contracts too, and twelve finance-specific columns (EBITDA, FCF, Debt Ratio, Coupon/Rate, Maturity, and others) are layered on top.

The twelve built-in workflows are deliberately untouched, deferred to Phase 11. The string-typed practice field and an "Others" fallback keep old values rendering in the meantime.

The rename reaches nine type identifiers, two filename renames, MIME types, the localStorage key, and the R2 bucket default. Two operational consequences follow. Deployments relying on the default R2 bucket name (mike) need to set R2_BUCKET_NAME explicitly before deploying. The localStorage key rename resets every existing user's last-selected model on their next visit - a one-time, silent state wipe.

LEGAL_NUMBERING_REF in shared/generateDocx.ts is intentionally not renamed; it points to Word's built-in numbering style called "legal," not to the legal domain. The rationale and other deferred decisions are logged in decisions.md.